4/24/13 11:37 AM EDT

A Senate committee vote on the confirmation of Labor nominee Thomas Perez was postponed after Republicans said they planned to invite a witness from a contentious whistleblower case to testify at a separate hearing Thursday.

The vote had also been scheduled Thursday, but is now set for May 8. The committee also postponed the hearing until further notice.

Committee Chairman Sen. Tom Harkin (D-Iowa) says he decided on the delay to give members more time to consider Perez's nomination. One of his aides said the hearing was postponed to avoid "political shenanigans" by GOP lawmakers.

The hearing, slated for the Subcommittee on Employment & Workplace Safety, was unrelated to the committee's Perez vote, but Democrats feared that by inviting the whistleblower, Republicans were trying to use it to thwart Perez's confirmation.

Republicans believe Perez, currently Civil Rights Division chief at the Department of Justice, in an attempt to get a favorable Supreme Court ruling in a separate case, essentially bargained away the administration's support for a lawsuit filed by whistleblower Frederick Newell against the City of St. Paul. Newell has slammed Perez for saying his case had no merit.

One GOP aide said Wednesday that within hours of notifying the committee that Newell would testify at the hearing, the committee postponed the hearing and the separate vote on Perez.

Republicans had previously asked that the vote on Perez be delayed, but Harkin initially denied the request before reversing course Wednesday.

“While I continue to believe there are no impediments to Mr. Perez’s confirmation, I am agreeing to postpone his Committee vote until May 8th, in order to allow those Senators who have asked the time to request additional information they believe they need, and to evaluate his qualifications," Harkins said in a statement provided to POLITICO Wednesday. "I am confident they will reach the same conclusion that I have, and that they will join the bipartisan array of business leaders, elected officials, civil rights leaders, and worker advocates that strongly support Mr. Perez’s confirmation.”

Harkin said the whistleblower case had nothing to do with the subject of the hearing, which was focused on OSHA whistleblowers. Newell was a whistleblower on St. Paul's alleged spending practices related to low-income employment.

"The Subcommittee was scheduled to meet to examine how weaknesses in OSHA whistleblower laws – which offer far fewer protections to workers than to whistleblowers who report on white-collar crime – put the lives and health of our nation’s workers at risk," Harkin said in the statement. "Rather than engage on this important topic, our Republican colleagues decided to use this as an opportunity to attack the President’s nominee for Secretary of Labor, Thomas Perez. I chose not to allow this abuse of process."